Genetic Engineering of Human Embryos – Further Information

genetic engineering of embryos

Below are links to topics about genetic engineering of human embryos as well as germline engineering. Click on the topic to go to that page.


DNA: The molecules in the body that are naturally inherited from parents and most strongly influence the body’s characteristics, development through life, and many tendencies for behavior.

The influences of DNA occur by interacting in various ways with protein molecules, often “instructing” the way protein is used. Protein is found in every cell of the organism and used to build new cells, repair cells, or create chemicals that affect the organism’s most fundamental processes.

There are four primary substances in DNA that are organized in long sequences in the shape of strands (chains). Each individual organism’s DNA has a unique pattern of these four substances.

Gene: A segment of DNA that, as a unified segment, has a particular effect on the organism. Some genes, for example, may cause a human body to have blue eyes, while other genes may influence behavior by causing an organism to have a physical drive to run away when attacked.

Genome: The entire sequence of genes in the DNA of an individual organism. Although every individual organism has a unique genome, scientists often talk about the genome of a species, which is the type and sequence of genes that are nearly identical within all individuals of that species, as well as a description of the genes and their places within DNA that often vary among individuals.

It is important to understand that it is rare to find a single gene that always has a specific effect on an organism, contributing to unpredictable effects of genetic engineering. Most characteristics or abilities that we can identify in organisms are “caused” by a number of genes that interact in complex ways, and often in ways that vary among individuals. Even a basic human characteristic like height is influenced by tens of thousands of genetic variations.

The influence of a single gene on the organism can change depending on the way it interacts with other genes, proteins, and bacteria.

One or more genes may also influence multiple characteristics, and usually do, making the unpredictable effects of genetic engineering very risky.

To complicate things further, the “expression” (active influence) of a gene can be turned on or off, or changed, by the nature of the entire DNA sequence.

Genes can mutate, which is when random “mistakes”, damage, or interaction with other substances interfere with the process of duplicating DNA in cells. The new DNA is not an exact copy of the original DNA.  

An individual’s genetic information in DNA can actually change during lifetime through their experiences. These changes may be inherited by children. The field of science that studies these lifetime changes in DNA is called epigenetics.

Finally, genes do not entirely determine a person’s nature. Environmental factors, damage, disease, and freely chosen acts of the organism can interfere with genes’ actual control over what the organism looks like or how it acts.

Understanding the influence of each gene on an organism is therefore an extremely complex task. There is no way to know if a gene or group of genes might have an effect that is unexpected. Even when research has shown a gene (or an edited gene) to have one consistent effect, an unexpected effect may appear in the millions of potential variations, mutations, and scenarios that occur as edited genes are inherited.


Genetic engineering is theoretically possible for any living organism.

Genetic engineering is a procedure that strategically changes an organism’s DNA – the molecules in the body that most strongly influence its characteristics, growth, and many tendencies for behavior. (Click here for background information on genes, DNA, and their unpredictable effects.)

Scientists have edited the genes of plants for a long time, and more recently on many animals. They have replaced genes in plants or animals with some genes of another species. For example, some human genes have been inserted in pigs’ DNA so the pigs’ organs can be successfully used to replace damaged organs in a human person’s body.

In this description of genetic engineering of human beings near the beginning of life, scientists hope to develop therapies that will remove unwanted genetic characteristics, or add or enhance desired characteristics, for the lifetime of an unborn person. In most research publicly reported so far, the characteristics targeted are diseases, abnormalities, or disabilities.

Some researchers and companies are more interested in highly profitable opportunities to increase capabilities like intelligence and strength, design characteristics like eye color and gender, and extend lifespan. Simple cosmetic therapies are certainly possible based on current knowledge, but enhancing capabilities like intelligence or character traits like empathy will be very complex. On the other hand, recent revelations about secret experiments have demonstrated how quickly researchers might stumble unexpectedly upon therapies that can enhance abilities like memory and efficient brain function.

The description of genetic engineering on this page refers only to engineering the DNA of unborn human beings in a laboratory, not to more limited therapies on adults. Researchers in human genetic engineering experiment on the DNA of animals, unborn human embryos (multi-cell unborn children up to the eighth week after conception), and more recently on human adults (called somatic cell genetic engineering).

The procedure used in genetic engineering technologies applies enzymes (usually proteins that accelerate chemical processes) to DNA in order to locate specific genes and either remove them from a strand of DNA or replace them with a different gene.

Targeted gene engineering has been performed for several years through tools called TALENs and ZFNs. A new tool for genetic engineering called CRISPR-Cas9 (an improved version of CRISPR that uses a particular enzyme) has only recently been used by researchers. This tool is much more accurate in identifying and engineering the targeted genes. It is also much faster, so genetic engineering therapies can be researched and put into practice within a short time. The fairly low cost of CRISPR-Cas9 enables scientists across the world to jump into research without the usual limits on funding from institutions and governments.

The human genetic engineering therapies that are being developed involve conceiving human beings through IVF (in vitro fertilization). Scientists create multiple human embryos by combining a woman’s eggs and man’s sperm in a laboratory dish, and a favored embryo is selected to avoid “defects” or sometimes to choose characteristics like eye color and gender. Unwanted embryos are destroyed, used in research, or frozen for possible future use. The selected embryo’s DNA will be edited. Then the edited embryo will be placed in a woman’s uterus so it can grow and be born.

Germline editing is the intentional change of inherited DNA through later generations. Genetic engineering is first performed on a single individual, and then it is hoped that the desired change in the individual will be passed to descendants so that it alters humanity permanently.

Germline editing is extremely difficult, because there is no guarantee that the hoped-for change will survive future mutations (unpredictable changes in DNA due to “mistakes” in copying new DNA or the effects of certain chemicals) or environmentally induced changes in DNA. The effects of editing genes can be highly unpredictable because there is no way to know if there are additional influences of genes and interaction of genes that may not have been known when the genetic engineering takes place. 

Even if scientists feel pretty confident that the possible effects of genetic engineering or germline editing are reasonably predictable, we can’t know for sure if random factors like the organism’s environment will interfere with or alter the actual influence of genes on the organism. Plus, the genetic information may change somewhat during an organism’s lifetime, potentially changing the expected effects in future generations.

It should be clear from even this basic description of genetic engineering that genetic engineering of unborn human beings raises important concerns, even from a purely secular point of view:

… Human embryos are killed in research and the IVF procedure.

… Whoever determines the goals of the genetic engineering therapy – parents, scientists, doctors, or government – acts according to their interests, values, conscience, biases, influences from others, or perception of what is good for the child. These motivators may not be morally or reasonably sound. Parents and their doctors may not consider the wisdom of others, act with correct information, or avoid the influence of biased opinions of peers and society.

… The unborn child cannot consent to the genetic alteration.

… The adults authorizing the genetic engineering have expectations that can be unwarranted or overly confident, and they may discount the risk of undesirable changes in the child. It is impossible for scientists to ever know fully whether genetic engineering will produce unexpected changes in future generations.


In the U.S. and elsewhere, new genetic engineering therapies will enable parents, doctors, and maybe even the government to take radical control over designing the nature of unborn human children. At this time, researchers are only at the experimental stage of developing therapies that can be regularly applied by scientists or for-profit businesses to unborn persons. Their progress, however, has been so rapid that therapies may be available to parents within a few years.

In November 2018, a researcher named He Jiankui shocked the world by declaring that twin baby girls had been born after he secretly edited their genes with the intention of reducing their vulnerability to HIV. Because the girls are born, they have the opportunity to someday procreate and pass down their altered genes to future generations. He Jiankui’s recklessness was made clear when scientists revealed that his tampering with the girls’ genes probably enhanced the ability of the girls to learn and form memories. In spite of the possible benefits to the girls, the brain enhancements were an accident caused by a gambling researcher who didn’t understand the full consequences of his actions. Genetic engineering in human beings can be highly unpredictable.

Targeted gene engineering has been performed for several years through tools called TALENs and ZFNs. A new tool for genetic engineering called CRISPR-Cas9 (an improved version of CRISPR) became available in 2012, and has only recently been used heavily in research. It is much more accurate in identifying and engineering the targeted genes. It is also much faster, so genetic engineering therapies can be researched and put into practice within a short time. The fairly low cost of CRISPR-Cas9 is enabling scientists across the world to jump into research without the usual limits on funding from institutions and governments.

So far, researchers in genetic engineering have concentrated most of their efforts on eliminating unwanted genetic “diseases”, such as Parkinson’s disease, a form of leukemia, HIV immunity, and inherited “abnormalities” or “disabilities”. As far as we know, no such therapy has been put into use for human embryos that are not destroyed before birth, although He Jiankui’s secret experiment and the birth of his subjects demonstrates the possibility for unknown experiments.

Some researchers and companies are more interested in highly profitable opportunities to increase capabilities like intelligence and strength, design characteristics like eye color and gender, and extend lifespan. Simple cosmetic therapies are certainly possible based on current knowledge, but enhancing capabilities like intelligence or character traits like empathy will be very complex. On the other hand, the unintended improvement of brain function in He Jiankui’s experiment demonstrates how quickly researchers might develop or stumble upon ways to deliberately enhance human beings.

Significant majorities of Americans support the development of human genetic engineering therapies. Here are results from a survey by AP-NORC on U.S. attitudes toward the purposes of gene-engineering technology:

  • 71% – Eliminating incurable, hereditary “diseases” (e.g. cystic fibrosis, Huntington’s disease).
  • 67% – Preventing “diseases” like cancer.
  • 65% – Preventing non-fatal conditions (e.g. blindness).
  • 12% – Enhancing abilities (e.g. intelligence, physical strength or athleticism).
  • 10% – Changing a physical attribute (e.g. eye color).

Despite the low survey responses in favor of enhancing abilities or cosmetic features, it is worth recognizing that many clinics that provide IVF procedures are currently meeting the interest of parents in selecting embryos with preferred cosmetic and gender characteristics. This suggests that similar demands will apply to opportunities through genetic engineering. Extremely high rates of aborting unborn children found to have unwanted genetic conditions or disabilities (around 90% for children with Down syndrome) indicate a widespread interest in discrimination against those characteristics, and such attitudes of parents and medical professionals will likely motivate use of genetic engineering therapies.


In the United States, there is no legal prohibition of privately funded genetic engineering research on human embryos, and research has been ongoing in the U.S. since 2017. The FDA (Food and Drug Administration) will not evaluate such research on unborn human beings, so the application of these genetic engineering therapies will not be approved. Federal law also prevents federal funding of research in which human embryos are “destroyed, discarded or knowingly subjected to risk of injury or death greater than that allowed for research of fetuses in utero” (The Dickey-Wicker Amendment most recently added to theOmnibus Appropriations Act, 2009, Title V, Sec. 509a ).

The NIH (National Institutes of Health), however, has indicated support for “in utero gene transfer clinical trials” once scientists achieve a more thorough understanding of the benefits and risks (NIH, Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules, April 2016, p. 100). The development of inexpensive tools like CRISPR-Cas9 has greatly reduced the need of private research institutions for government funding.

The U.S. government is also legally bound to honor certain international treaties that impact genetic engineering research and application of therapies. The U.S. Congress ratified the International Convention on the Elimination of All Forms of Racial Discrimination, the Convention Against Torture, and the Genocide Convention. Treaties signed but not ratified include the Convention on the Rights of the Child, the Convention on the Rights of Persons with Disabilities, and the International Covenant on Economic, Social, and Cultural Rights.

These treaties base human rights on the “dignity of the human person,” but they do not include unborn human beings in the definition of a “person” with full rights. The treaties mandate such rights as protection from discrimination, torture, genocide, and non-consensual experimentation. They declare individual rights to access to healthcare, identity (civil status), right to life of children, physical integrity of one’s body, equal enjoyment of the fruits of science and technology, the “inherent dignity and individual autonomy including the freedom to make one’s own choices,” “respect for difference and acceptance of persons with disabilities as part of human diversity and humanity”, and “respect for the right of children with disabilities to preserve their identities.” (Convention on the Rights of Persons with Disabilities, 2006, Art. 3 General Principles.)

If unborn human beings were ever to be included under the definition of a “person”, these treaties would likely be interpreted as prohibiting genetic engineering on human embryos. Many of the rights would interfere with such genetic engineering if they were interpreted widely and strictly, but there is little indication that governments will apply the treaties in that way. 

The Genocide Convention defines genocide as including serious bodily harm, prevention of births, and physical destruction of protected groups. The International Covenant on Economic, Social, and Cultural Rights defines the right to health as “the right to control one’s health and body, including sexual and reproductive freedom, and the right to be free from interference, such as the right to be free from torture, non-consensual medical treatment, and experimentation.” This definition was further explained by the UN Special Rapporteur as “the right of access to appropriate health care services that will enable women to go safely through pregnancy and childbirth and provide couples with the best chance of having a healthy infant.” Since children and unborn humans are not considered “persons” with full rights, it is the parents’ right of reproductive freedom that will likely hold priority according to legal professionals and courts. “Reproductive freedom” will probably enable parents to engage in genetic engineering of their child.

A 2009 United Nations report examined the laws of 192 countries and found that 133 of them did not have any regulation of human genetic engineering technologies. On the other hand, no country currently has a law that explicitly legalizes germline engineering through the birth of genetically edited embryos, and over 40 countries, including those in the European Union, explicitly ban it. The laws in other countries are often quite vague and possibly unenforceable. Some countries like China have not effectively enforced their regulations.

Some scientifically advanced and wealthy countries have begun to reject the international consensus and embrace human genetic engineering research. This puts enormous pressure on other countries to compete economically by allowing the research. In 2016, the United Kingdom explicitly legalized genetic engineering experiments on human embryos for institutions that are licensed to do so. The embryos must be destroyed after 14 days. The Canadian Institutes of Health Research, a government agency, is pushing to reverse a law that prohibits genetic engineering research on embryos.

European countries have jointly developed the international laws that are most relevant to human genetic engineering, but they only apply in Europe minus the United Kingdom. They will likely have a strong influence on any new international legal framework. The laws include the Universal Declaration on the Human Genome and Human Rights, the Convention for the Protection of Human Rights and Dignity of the Human Being with Regard to the Application of Biology and Medicine, and the Additional Protocol on the Prohibition of Cloning Human Beings. The European laws attempt to protect the uniqueness of individuals’ DNA, diversity, the right not to become a product for others’ profit, and the right to enjoy the fruits of scientific progress in society. Regarding human germline editing, extreme caution should be used to protect future generations, and it is banned for the time being. European law strongly prohibits eugenics, understood as a broad effort to eliminate or prevent the birth of a large segment of the population. Many goals of human genetic engineering might potentially be violations of the laws against eugenics, but there has not yet been such a legal challenge or determination.


WHO (World Health Organization) formed an 18-member commission that will meet in March 2019 to form influential guidelines for the world’s scientists and researchers in human genetic engineering. The commission does not include any persons who pay scholarly attention to religious perspectives. The WHO guidelines will not be enforceable as law, but will inform new treaties and the laws of individual countries.

The U.S. National Academies of Science (NAS) published a report in 2017 that claimed “there is a need for caution in any move toward germline engineering, but that caution does not mean prohibition” when research on the risks has advanced sufficiently. Although equally cautious for the time being, the National Academies of Sciences, Engineering, and Medicine and the Nuffield Council on Bioethics in the United Kingdom have expressed enthusiasm for the possibility of germline engineering.

Scientists and secular bioethicists focus their moral evaluation of human genetic engineering research on standard principles such as obtaining clear consent from the parents (if parents are involved in creating new embryos), following national laws, and focusing only on “medical” goals. Major associations of scientists, research universities, and prominent bioethics scholars (those not writing from a religious perspective) do not acknowledge any moral concerns with engineering and destroying unborn humans. Nearly all oppose the birth of genetically edited humans until much more is known about the effects of such engineering on future generations.   

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